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This manual page explains the groff an.tmac macro package (often called
the man macro package). This macro package should be used by developers
when writing or porting man pages for Linux. It is fairly compatible with
other versions of this macro package, so porting man pages should not be a
major problem (exceptions include the NET-2 BSD release, which uses a totally
different macro package called mdoc; see mdoc(7)).

Note that NET-2 BSD mdoc man pages can be used with groff simply by
specifying the -mdoc option instead of the -man option. Using
the -mandoc option is, however, recommended, since this will
automatically detect which macro package is in use.

For conventions that should be employed when writing man pages for the Linux
man-pages package, see man-pages(7).

The only mandatory heading is NAME, which should be the first section and be
followed on the next line by a one-line description of the program:

.SH NAME

item \- description

It is extremely important that this format is followed, and that there is a
backslash before the single dash which follows the item name. This syntax is
used by the mandb(8) program to create a database of short descriptions
for the whatis(1) and apropos(1) commands. (See
lexgrog(1) for further details on the syntax of the NAME section.)

For a list of other sections that might appear in a manual page, see
man-pages(7).

Bold alternating with Roman (especially useful for
referring to other manual pages)

.I

Italics

.IB

Italics alternating with bold

.IR

Italics alternating with Roman

.RB

Roman alternating with bold

.RI

Roman alternating with italics

.SB

Small alternating with bold

.SM

Small (useful for acronyms)

Traditionally, each command can have up to six arguments, but the GNU
implementation removes this limitation (you might still want to limit yourself
to 6 arguments for portability's sake). Arguments are delimited by spaces.
Double quotes can be used to specify an argument which contains spaces. All of
the arguments will be printed next to each other without intervening spaces,
so that the .BR command can be used to specify a word in bold followed
by a mark of punctuation in Roman. If no arguments are given, the command is
applied to the following line of text.

Below are other relevant macros and predefined strings. Unless noted otherwise,
all macros cause a break (end the current line of text). Many of these macros
set or use the "prevailing indent." The "prevailing
indent" value is set by any macro with the parameter i below;
macros may omit i in which case the current prevailing indent will be
used. As a result, successive indented paragraphs can use the same indent
without respecifying the indent value. A normal (nonindented) paragraph resets
the prevailing indent value to its default value (0.5 inches). By default, a
given indent is measured in ens; try to use ens or ems as units for indents,
since these will automatically adjust to font size changes. The other key
macro definitions are:

Start relative margin indent: moves the left margin
i to the right (if i is omitted, the prevailing indent value
is used). A new prevailing indent is set to 0.5 inches. As a result, all
following paragraph(s) will be indented until the corresponding
.RE.

.RE

End relative margin indent and restores the previous value
of the prevailing indent.

Begin paragraph with a hanging indent (the first line of
the paragraph is at the left margin of normal paragraphs, and the rest of
the paragraph's lines are indented).

.IP x i

Indented paragraph with optional hanging tag. If the tag
x is omitted, the entire following paragraph is indented by
i. If the tag x is provided, it is hung at the left margin
before the following indented paragraph (this is just like .TP
except the tag is included with the command instead of being on the
following line). If the tag is too long, the text after the tag will be
moved down to the next line (text will not be lost or garbled). For
bulleted lists, use this macro with \(bu (bullet) or \(em (em dash) as the
tag, and for numbered lists, use the number or letter followed by a period
as the tag; this simplifies translation to other formats.

.TP i

Begin paragraph with hanging tag. The tag is given on the
next line, but its results are like those of the .IP command.

Insert a hypertext link to the URI (URL) url, with
all text up to the following .UE macro as the link text.

.UE [trailer]

Terminate the link text of the preceding .UR macro,
with the optional trailer (if present, usually a closing
parenthesis and/or end-of-sentence punctuation) immediately following. For
non-HTML output devices (e.g., man -Tutf8), the link text is
followed by the URL in angle brackets; if there is no link text, the URL
is printed as its own link text, surrounded by angle brackets. (Angle
brackets may not be available on all output devices.) For the HTML output
device, the link text is hyperlinked to the URL; if there is no link text,
the URL is printed as its own link text.

These macros have been supported since GNU Troff 1.20 (2009-01-05) and Heirloom
Doctools Troff since 160217 (2016-02-17).

Although technically man is a troff macro package, in reality a large
number of other tools process man page files that don't implement all of
troff's abilities. Thus, it's best to avoid some of troff's more exotic
abilities where possible to permit these other tools to work correctly. Avoid
using the various troff preprocessors (if you must, go ahead and use
tbl(1), but try to use the IP and TP commands instead for
two-column tables). Avoid using computations; most other tools can't process
them. Use simple commands that are easy to translate to other formats. The
following troff macros are believed to be safe (though in many cases they will
be ignored by translators): \", ., ad, bp,
br, ce, de, ds, el, ie, if,
fi, ft, hy, ig, in, na, ne,
nf, nh, ps, so, sp, ti, tr.

You may also use many troff escape sequences (those sequences beginning with \).
When you need to include the backslash character as normal text, use \e. Other
sequences you may use, where x or xx are any characters and N is any digit,
include: \', \`, \-, \., \",
\%, \*x, \*(xx, \(xx, \$N, \nx,
\n(xx, \fx, and \f(xx. Avoid using the escape sequences
for drawing graphics.

Do not use the optional parameter for bp (break page). Use only positive
values for sp (vertical space). Don't define a macro (de) with
the same name as a macro in this or the mdoc macro package with a different
meaning; it's likely that such redefinitions will be ignored. Every positive
indent (in) should be paired with a matching negative indent (although
you should be using the RS and RE macros instead). The condition
test (if,ie) should only have 't' or 'n' as the condition. Only
translations (tr) that can be ignored should be used. Font changes
(ft and the \f escape sequence) should only have the values 1,
2, 3, 4, R, I, B, P, or CW (the ft command may also have no parameters).

If you use capabilities beyond these, check the results carefully on several
tools. Once you've confirmed that the additional capability is safe, let the
maintainer of this document know about the safe command or sequence that
should be added to this list.

By all means include full URLs (or URIs) in the text itself; some tools such as
man2html(1) can automatically turn them into hypertext links. You can
also use the UR and UE macros to identify links to related
information. If you include URLs, use the full URL (e.g.,
http://www.kernel.org
to ensure that tools can automatically find the URLs.

Tools processing these files should open the file and examine the first
nonwhitespace character. A period (.) or single quote (') at the beginning of
a line indicates a troff-based file (such as man or mdoc). A left angle
bracket (<) indicates an SGML/XML-based file (such as HTML or Docbook).
Anything else suggests simple ASCII text (e.g., a "catman" result).

Many man pages begin with ´\" followed by a space and a list
of characters, indicating how the page is to be preprocessed. For
portability's sake to non-troff translators we recommend that you avoid using
anything other than tbl(1), and Linux can detect that automatically.
However, you might want to include this information so your man page can be
handled by other (less capable) systems. Here are the definitions of the
preprocessors invoked by these characters:

Most of the macros describe formatting (e.g., font type and spacing) instead of
marking semantic content (e.g., this text is a reference to another page),
compared to formats like mdoc and DocBook (even HTML has more semantic
markings). This situation makes it harder to vary the man format for
different media, to make the formatting consistent for a given media, and to
automatically insert cross-references. By sticking to the safe subset
described above, it should be easier to automate transitioning to a different
reference page format in the future.

This page is part of release 4.15 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the latest
version of this page, can be found at
https://www.kernel.org/doc/man-pages/.